Method and device for regulating the temperature of a drive element

ABSTRACT

The invention relates to a device ( 11 ) and a method of regulating a temperature of a drive element ( 2 ) which can be employed in a deep-freezing application in particular, such as a band, belt or similar, in which at least a part-region of the drive element ( 2 ) is heated at least during a relative displacement between the drive element ( 2 ) and a machine part. The drive element ( 2 ) is adjusted to a pre-definable minimum temperature and a pre-settable minimum temperature is maintained. To this end, the device ( 11 ) has at least one module ( 12 ), which supplies the drive element ( 2 ) with mechanical, electrical or electromagnetic energy, for example.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicants claim priority under 35 U.S.C. §119 of AUSTRIAN ApplicationNo. A 822/01 filed on May 23, 2001. Applicants also claim priority under35 U.S.C. §365 of PCT/AT02/00153 filed on May 17, 2002. Theinternational application under PCT article 21(2) was not published inEnglish.

The invention relates to a method of regulating the temperature of adrive element which is used in applications involving deep-freezing inparticular, and a device for implementing this method, having thefeatures defined in the generic parts of claims 1 and 22.

Productivity, cost pressures and time factors demand high availabilityand low cycle times of moving units, especially when used indeep-freezing applications. These requirements demanded of moving unitsand their driving elements have generally been satisfied in the past byusing chain drives to generate a linear feed motion which can operate attemperatures of from 0° C. to approximately −80° C., for example,without their function being adversely affected. With the advent ofmodern, automated technology, however, such chain drives soon reachedtheir limits due to their large dimensions and associated potentialoperating speeds, which are limited, as well as their loud noise and thestress generated due to impacts and vibrations induced during operation.Being made of simple construction means, they are only suitable forstructures of a limited size and require a lot of maintenance iffault-free operation is to be guaranteed.

In more recent years, it has been suggested that chain drives should bereplaced by belt drives, which are made from plastic materials with alow Shore hardness in order to retain their elasticity, even at very lowtemperatures. The realisation that belt drives were a viable optionimmediately offered the-advantage of being able to operate moving unitsat higher speeds, although it was evident that belts of a specific Sorehardness would have to be used for different temperature ranges, inorder to keep to a minimum the wear caused by brittleness, which isinduced in particular by feeding rigid belt drives at increasingly highspeeds round return pulleys at low temperatures. Accordingly, it becamestandard practice to use low Shore hardness values in order to counterthis effect but this measure brought a disadvantage due to the fact thatit increased the elasticity of the belts, especially when exposed totemperature fluctuations, which meant that optimum transmission of thedriving forces and torques could no longer be achieved.

Accordingly, the objective of the invention is to avoid the knowndisadvantages of the prior art and to do so without having to modify ormodifying only slightly the production conditions under which driveelements are required to operate, whilst preserving optimum propertiesin the drive element, even when used in applications involving very lowor sharply fluctuating temperatures.

This objective is achieved by the invention as a result of the methoddefined by the characterising features of claim 1. The advantage of thismethod resides in the fact that a method based on simple laws of physicsis used to regulate the temperature of a drive element, such as a beltor band, by means of which such drive elements can also be operated attemperatures of between 0° C. and −40° C., for example, whilstpreserving the properties needed to guarantee dynamic operation of themoving unit within a plant in terms of factors such as acceleration,feed rate, etc. Even temperature fluctuations of between +15° C. and−40° C., for example, have no effect on the elasticity and strength ofthe driving element and hence the dynamics, e.g. acceleration, feedrate, of a drive mechanism used with moving units.

Other advantageous features which enable a pre-definable minimumtemperature of the drive element in the range of approximately +5° C. to+25° C., in particular +10° C. to +22° C., e.g. +20° C., to be adjusted,set and maintained are specified in claims 2 to 7. The various featuresspecified in the claims enable optimum adaptation and control of thetemperature to suit different applications, for which purpose theminimum temperature is preferably obtained by delivering the requisiteenergy by means involving no contact in the case of endlesslycirculating drive elements and by means involving contact in the case ofnon-endless drive-elements, and the module and energy or power to bedelivered is specifically adapted and set for a specific type of driveelement and/or making allowance for ambient influencing factors. Moreparticularly the features specified in claim 7 now enable the use ofdrive elements of large dimensions and in spite of the fact that thedrive element might have a large cross section, it is neverthelesspossible to obtain a uniform distribution of heat or temperature throughits cross-section and length, e.g. +20° C. Another advantage is the factthat the measures proposed by the invention can be used with themajority of drive systems known from the prior art.

Claims 8 to 10 define advantageous measures and features, whereby, evenafter longer periods of down time, it is now possible to start up amoving unit and immediately run it up to a high level of performancebecause the drive element can be pre-heated at least over a part of itslength shortly before switching on the moving unit if necessary, and thetemperature increased on a substantially continuous basis after andduring operation. A pre-set temperature increase up to a pre-settableminimum temperature can be reached automatically within a specific timeand this minimum temperature can then be kept at least almostsubstantially constant, at least for the period during which the movingunit is in operation using measuring means and appropriate controlalgorithms, which helps to improve the level of efficiency andproductivity of moving units.

The embodiment of the method specified in claims 11 to 13 is also ofadvantage since it provides a simple means of installing and/orretrofitting on site the module needed to deliver the energy without theneed for particularly complex systems, whilst additionally offering thepossibility of being able to adapt to different requirements, such asthe temperature range, the material from which the drive element ismade, the installation area, etc., for example.

The features defined in claims 14 and 15 ensure a uniform temperaturedistribution and temperature control in and around the drive element,which in turn guarantees that the moving unit will exhibit uniformdynamic behaviour during operation and, in a broader sense, less stresson the mechanical construction.

As a result of the embodiments defined in claims 16 to 18, the effect ofconverting electric power into heat achieved by passing a currentthrough an ohmic resistance is used as a means of obtaining a uniformtemperature distribution in the drive element.

Also of advantage are the features specified in claims 19 to 21, wherebythe temperature of the drive element, ambient conditions, circulationspeed, feed rate, etc., are detected on at least certain sections andfor certain periods of time, etc., so as to forward and/or output ameasurement variable and an actual value which can be applied as a meansof controlling the minimum temperature of the drive element via acontrol system. This enables very accurate adaptation, especially wheredrive units are used in highly sensitive areas. In particular, thismeasurement variable may also be primarily used as a means ofcontrolling the frequency setting on the basis of a defined controlalgorithm, for example, thereby establishing a closed-loop automaticcontrol circuit.

The objective of the invention is also achieved by means of the featuresdefined in claim 22. The surprising advantage of this approach is thatsystems that have been tried and tested in practice in terms of thedrive element and the module can be used for regulating the temperatureof the drive element, and these are not only inexpensive to manufacturebut have also proved themselves to be the best possible solutions.

The embodiments defined in claims 23 to 26 enable the use ofstandardised, inexpensive and sufficiently proven modules, such asinduction coils, microwave generators, heating devices or similar to beused, which makes the system proposed by the invention by the inventionhighly reliable, especially the module. Another major advantage is thefact that the individual modules already have the optimum specificationsand are mostly already relatively small in terms of their dimensions, sothat the space needed to accommodate the system proposed by theinvention can be kept to a minimum.

The advantage of the embodiments defined in claims 27 to 30 is that thestrengthening supports which have to be provided in the drive elementsas a matter of course anyway serve as the ohmic resistance which isvital as a means of dissipating heat, permitting the use of all driveelements known from the prior art which are also capable of transmittinghigh driving forces.

As a result of the embodiment defined in claim 31, the strengtheningsupports provided in the belt act as an electromagnetic conductive core,which helps to produce a further increase in flow density and hence thevoltage or current induced in the loop.

Advantages are also to be had by using aramide or steel fibres or glassfibres for the strengthening supports, as described in claim 32.

The embodiments defined in claims 33 and 34 offer embodiments of simpleconstruction designs for inducing the voltage or current needed tochange the magnetic flow, in the former case when using alternatingvoltage and in the latter case when using direct voltage. Varying theoverlap between the module and the drive element, which determines flowdensity, enables the magnetic flow to be influenced as required, therebyensuring optimum adaptation to different applications.

In another embodiment defined in claim 35, the module is provideddirectly in or on the casing which has to be provided for safety reasonsin any event, offering the possibility of improving temperatureregulation still further because the surface area which is decisive withregard to changing the magnetic flow can be increased to a maximum.

The embodiment defined in claim 36 permits the use of standardised,inexpensive induction coils.

Another embodiment defined in claim 37 offers another reliable solutionto regulating the temperature in the drive element and provides a simplemeans of maintaining a pre-settable minimum temperature because,although the drive element incorporates at least one passage, it isnevertheless very simple to manufacture and co-operates with the moduleso that the temperature of the drive element can be regulated rapidlyand a minimum temperature set, in particular an operating temperature,even under the harshest conditions.

This being the case, other embodiments defined in claims 38 to 41 may beused, which allow the system proposed by the invention to be employedwith different systems, in particular endless and non-endless driveelements.

The design proposed by the invention is primarily suitable for use withall flat belts, V-belts or cogged belts of various structures known fromthe prior art, as described in claims 42 and 43.

As a result of the embodiment defined in claim 44, the temperatureprevailing in or at the drive element can be immediately detected, usingtried and tested yet inexpensive systems known from the prior art, whichmeans that the drive element can be monitored on a permanent basis ifnecessary.

Finally, the embodiment defined in claim 45 is also of advantage becauseby pre-defining a control algorithm and the actual value input for thetemperature via the measuring means and optionally entering a defaultsetting for the ambient temperature, a pre-definable minimum temperatureoptimised for these conditions can be set or predefined, after which apermanent control of the actual value of the temperature can be run onthe basis of the control algorithm and the detected parameters appliedto the closed-loop control circuit.

The invention will be described in more detail with reference to theexamples of embodiments illustrated in the appended drawings.

Of these:

FIG. 1 is a highly simplified, schematic diagram showing a side view ofa device as proposed by the invention with a conveyor unit and apower-generating module;

FIG. 2 is a highly simplified, schematic diagram in section along theline II—II indicated in FIG. 1 of a drive element of the moving unit;

FIG. 3 is a highly simplified diagram in section along line III—IIIindicated in FIG. 1 of the power-generating module;

FIG. 4 is a highly simplified, schematic diagram showing a plan view ofanother embodiment of the device proposed by the invention, with themoving unit and the power-generating module;

FIG. 5 is a highly simplified, schematic diagram in partial section,showing another embodiment of the drive element and module;

FIG. 6 is a highly simplified, schematic diagram depicting anotherembodiment of the device proposed by the invention, with the moving unitand the power-generating module;

FIG. 7 is a highly simplified, schematic diagram showing a side view ofthe device proposed by the invention, with the moving unit and adifferent embodiment of the power-generating module;

FIG. 8 is a highly simplified, schematic diagram in section along lineVIII—VIII indicated in FIG. 7, showing the module and a belt pulley withthe drive element;

FIG. 9 is a highly simplified, schematic diagram showing a side view ofanother embodiment of the device proposed by the invention, with themoving unit and a different embodiment of the power-generating module,this time incorporating an illustrative array of several modules.

Firstly, it should be pointed out that the same parts described in thedifferent embodiments are denoted by the same reference numbers and thesame component names and the disclosures made throughout the descriptioncan be transposed in terms of meaning to same parts bearing the samereference numbers or same component names. Furthermore, the positionschosen for the purposes of the description, such as top, bottom, side,etc,. relate to the drawing specifically being described and can betransposed in terms of meaning to a new position when another positionis being described. Individual features or combinations of features fromthe different embodiments illustrated and described may be construed asindependent inventive solutions or solutions proposed by the inventionin their own right.

FIGS. 1 to 3, which will be described together, illustrate differentviews of a moving unit 1 incorporating a belt-type drive element 2. Asillustrated in the embodiment chosen as an example here, the driveelement 2 is of an endless design and is driven by at least one drivingmember 3 and turned back around at least one driven member 4. As amachine part, the driving member 3 is fixed in its position relative tothe drive element 2, whilst the drive element 2 is displaceable relativeto it. The driving and driven members 3, 4 are provided in the form of apulley wheel seated respectively on a driving shaft and a driven shaft.The driving member 3, which is driven by a motor system, notillustrated, transmits the rotary force between the drive element 2 andthe driving member 3 by means of frictional and/or positive force.Accordingly, the drive element 2 may be provided in the form of a flatbelt or V-belt or cogged belt of any type. In this particularembodiment, the drive element 2 is provided as a flat belt. When rotaryforce is applied to the drive element 2, it is displaced in a forwardmotion in a pre-definable direction of rotation, which can be reversedby the drive motor, not illustrated, for example in the directionindicated by arrow 5.

The skilled person will be familiar with the structure of these driveelements 2, such as bands, belts, conveyor belts, and only a briefdescription of them is therefore necessary. As illustrated in FIG. 2,the drive element 2 has a running layer 6 facing the driving and drivenmembers 3, 4, a top layer 7 remote from the latter and a traction layer8 disposed between the two. Strengthening supports 9 are preferablyprovided in the drive element 2, preferably in the region of thetraction layer 8, extending parallel with one another and preferablyrunning across the entire length of the drive element 2. Thestrengthening supports 9 may be made from any materials known from theprior art, such as polyester, polyamide, steel and glass fibres oraramide, for example. If the strengthening supports 9 are made fromaramide and/or steel and/or glass fibres, the circulating strengtheningsupports 9 constitute an electrically conductive loop 10 or line. Thestrengthening supports 9 may be made in the form of a steel cable, forexample, with several strands. The running, top and traction layers 6,7, 8 may be made from different or identical materials, such as thosewhich have been used as standard in the prior art for some time. Thesame also applies to the geometric shape of the strengthening supports9. Accordingly, these may be helical, for example.

Especially if the moving unit 1 incorporating the drive element 2 is tobe used at low temperatures, more especially in applications involvingfreezing and deep-freezing, for example at 0° C. and −80° C., or in lowambient temperatures such as between 0° C. and −40° C. for example, itwill be necessary to regulate the temperature of or heat the driveelement 2 to a pre-defined minimum temperature, in order to ensure thatthe moving unit 1 is sufficiently dynamic, even at these lowtemperatures. Consequently, a device 11 of the type illustrated in FIG.1 is proposed, incorporating at least one module 12 which transmits ordelivers energy without making contact, provided in the form of aninduction system, in particular an induction coil 13, in this particularembodiment. This module 12 is expediently linked to a control unit 15via a connecting line 14 to enable parameters, data, signals andinformation to be transmitted. In the most basic situation, thisconnecting line 14 might be a two-wire line or a bus line. A controlunit 15 of this type used to activate the module 12, in particular theinduction coil 13, is known per se and is therefore only symbolicallyindicated as a box-shaped body. The control unit 15 additionally hascontrol and automatic control means as well as a control algorithm. Themodule 12, or as is the case in this embodiment modules 12, of thedevice 11 are stationary relative to the endlessly circulating driveelement 2 and extend across at least a part of the length of the driveelement 2. The modules 12 may be disposed in the region of thenon-driving free length and/or the tight side adjacent to the runningand/or top layer 6; 7 and/or extending through a thickness of the driveelement 2. The drive element 2 in the embodiment illustrated in FIG. 3is moved past or through two energy fields 16. Naturally it would alsobe possible to provide only one module 12 and induction system, inparticular one induction coil 13, and feed the drive element 2 throughone energy field 16. However, this embodiment is not illustrated. Themodule 12 is designed with a substantially U-shaped or C-shaped crosssection extending across a part of the length of the drive element 2 andat least more or less encases the drive element 2.

At least the stationary induction coil 13, to which alternating currentis applied, is provided in the form of a network-side primary windingand induces current or voltage in at least one strengthening support 9made from an electrically conductive material and constituting thesecondary winding, due to the changing magnetic flow. Various measuresknown from the prior art could naturally be employed as a means ofstrengthening the energy field 16 or increasing the magnetic flow, suchas using ferromagnetic materials, for example an iron core. A distanceor air gap between the drive element 2 and module 12 should be kept asshort as possible.

As a result of the displacement of the drive element 2 relative to themodule 12 and hence the energy field 16, in particular theelectromagnetic field, a uniform, pre-definable minimum temperature canbe generated and maintained essentially across the entire length andcross-section of the drive element 2. As a result of the invention, itis now possible for the drive element 2 to be warmed or heated to apre-defined minimum temperature during a relative displacement betweenit and the at least one module 12 by supplying energy. The variablesused as settings for the primary-side induction coil 13 energised withalternating current are primarily-the frequency and optionally thecurrent amplitude. The electromagnetic energy field 16 is generated bythe induction coil 13 operated in the medium- or high-frequency range,this frequency range being between 1 kHz and 150 kHz, for example 50kHz.

Energising the drive element 2 and the electrically conductivestrengthening supports 9 with the energy field in certain sections andfor certain periods of time, at least in a part-region of the driveelement 2, generates heat due to dissipation, which depends inparticular on the frequency of the primary-side induction coil 13. Thecontrol unit 15 is configured so that the frequency is set, for example,depending on the rotation speed of the drive element 2 and/or thetemperature to which the drive element 2 is exposed and/or an actualvalue of the temperature determined by a measuring means 17, for examplea thermocouple, pyrometer, which detects the temperature withoutinvolving any contact. The drive element 2 may be equipped withmeasuring means 17 disposed in different regions of the drive element 2and spaced at a distance apart from one another in its lengthwaysdirection in order to detect the actual value of the temperatureintermittently at specific points. These individually detected actualvalues of temperature are forwarded to the control unit 15, where theyare used to derive the arithmetic mean value of the temperature with aview to automatically applying parameters, such as the frequency of theinduction coil 13 or a microwave generator, the heat output of a module12 transmitting energy without contact and the amplitude of the currentflowing through the strengthening supports 9. These individualparameters are determined using drive motors known from the prior art,incorporating incremental transmitters and other sensor systems, such astemperature sensors, strain gauges, thermocouples, for example. Thesensor systems used to detect ambient influences, such as air humidity,ambient temperature, etc., are arranged in the general surrounding area,i.e. in the room where the moving unit 1 is installed, and are connectedto the control unit 15 to permit data transmission. Measuring means 17are provided on or in the drive element, in order to determine theactual value of its temperature. The actual value of the temperature ofthe drive element 2 may be detected in the running layer 6 and/or in thetop layer 7 and/or traction layer 8 and each of the individualmeasurement values is forwarded to the control unit 15 so that a controlvariable for the parameter can be determined. Alternatively, the actualvalue of the temperature may also be detected by other means which donot involve contact.

The operating factors which have to be set, such as the requisite drivedynamics, e.g., acceleration of a machine part, as indicated in FIG. 4,or rotation speed of the drive element 2 etc., and the driving behaviourof the moving unit 1, and/or the minimum temperature or operatingtemperature of the drive element 2, are determined automatically and setas an optimum value by the control unit 15 or as a variable value by anoperator, for example. In order to enter a default for and automaticallyset the minimum temperature, at least one ambient factor, such as theambient temperature and/or the air humidity and/or at least one of theoperating factors such as the coefficient of friction between the driveelement 2 and at least the driving member 3, or the acceleration of themachine part, is processed and taken into account as part of a controlprocess in an automatic control system such as a fuzzy logic,neuro-fuzzy systems etc. The option of being able to adjust and adaptthe minimum temperature to a specific application enables the dynamicbehaviour of the moving unit 1 to be improved significantly andsubstantially reduces the wear behaviour of the drive element 2. Aboveall, the method proposed by the invention makes it possible to react totemperature fluctuations.

It should be pointed out at this stage that the energy field 16 need notnecessarily be generated by means of the essentially inductive elementsdescribed above and the energy field 16 may also be generated bycapacitive elements instead, such as capacitors, in which case the driveelement 2 will be fed through the electric field generated. The electricfield generated is used to supply the energy needed to adjust ormaintain the pre-definable temperature of the drive element 2.

The moving unit 1 in this embodiment is a conveyor unit such as aload-bearing conveyor for individual items, etc., or a drive unit fordriving machinery. If the temperature-regulated drive element 2 isprovided in the form of a cogged belt, it may be designed as a timingchain used for determining the displacement path of a carriage, etc.,for example.

FIG. 4 illustrates another embodiment of the moving unit 1 with thebelt-type drive element 2. In this embodiment, the energy is deliveredand transmitted by a system involving contact. The drive element 2, inparticular the cogged belt, is of the non-endless type and extendsbetween two bearing and retaining mechanisms 18 spaced at a distanceapart from one another, to which its oppositely lying end regions 19 arelinked. The moving unit 1 in the embodiment illustrated as an examplehere is a linear unit with a machine part 20 which can be displacedrelative to the drive element 2, which is displaceable or slidable bymeans of the driving member 3 indicated by broken lines. The machinepart 20 is guided by means of a schematically indicated guide mechanism21 and is slidingly positioned by means of guide rods 22 forming theguide mechanism 21. Naturally, this design of the guide mechanism 21 ismerely given as an example and any other guide mechanism 21 known fromthe prior art could also be used.

A support strip 23 is preferably provided on a side of the drive element2 remote from the machine part 20, extending across at least a part ofthe length of the drive element 2, which absorbs the rotary forcestransmitted by the driving member 3 in a direction at an angle orperpendicular to the drive element 2. The machine part 20 has at leastone module 12, which is preferably disposed at a short distance from thedrive element 2 and is preferably provided in the form of an inductioncoil 13. The machine part 20 might be the module 12. The primary-sideinduction coil 13 of the machine part 20 energised with alternatingcurrent induces current or voltage in the loop formed by thestrengthening supports 9 and the electrical attenuation which occurs asthe current flows through the strengthening supports 9 is converted intoheat. An iron core may be provided between the primary-side inductioncoil 13 and the secondary-side loop 10 as a means of increasing themagnetic flow, for example. A part-region of the machine part 20 mayserve as this core. Another possibility of improving inductive heatingis to provide an iron core on the machine part 20 which extends aroundat least certain regions of the drive element 2 but preferably all sidesof it, for example, on a side of which the primary-side induction coil13 is disposed, whilst the secondary winding incorporating at least onewinding or loop 10, which may or may not be short-circuited, is providedon the oppositely lying side. This will mean that the input-sidefrequencies, in particular low frequencies, of the primary-sideinduction coil 13 can be kept low.

Although not illustrated, another possible embodiment of thestrengthening supports 9 is one in which it has at least one winding andwhen a direct voltage is applied to terminal contacts, the strengtheningsupports 9 essentially act as a heating element, enabling thepre-definable minimum temperature to be set and/or maintained in thestationary drive element 2.

FIG. 5 illustrates another embodiment, which may be construed as anindependent solution in its own right. Illustrated in cross-section, thedrive element 2 of the moving unit 1 has one or more layers, inparticular the running layer 6, top layer 7 and traction layer 8, andthe traction layer 8 is optionally provided with the strengtheningsupports 9 and at least one passage 24, which contains a liquid 25 witha high boiling point. A module 12 which generates wave power, inparticular microwave energy, co-operates with the drive element 2.Microwave generators of this type are already known from the prior art.As proposed by the invention, the temperature of the drive element 2 isregulated and the pre-definable minimum temperature is set andmaintained due to the fact that the liquid 25 with a high boiling pointis contactlessly irradiated with microwave energy so that it and thedrive element 2 are heated, at least in the region where the passage 24is located. The passage 24 expediently extends along the entire lengthof the drive element 2. This drive element 2 may be either endless or ofa non-endless design. Another possible approach is one in which thestrengthening supports 9 have a coil so that when a direct voltage isapplied, the strengthening supports 9 essentially act as a heatingelement, so that energy is transmitted in a controlled manner to theheat-transmitting liquid. This feature enables the temperature of evenmore robust drive elements 2 to be regulated. If the drive element 2 hasa thick cross section, passages 24 may be provided in several planes oneabove the other.

FIG. 6 provides a highly simplified, schematic diagram illustratinganother embodiment of the device 11, in particular the module 12. Asdescribed above in connection with the other drawings, the moving unit 1has at least one driving member 3 and at least one driven member 4, bymeans of which the endlessly circulating drive element 2 is driven at apre-definable rotation speed and feed path or displacementdirection—indicated by arrow 5. In this embodiment, the drive element 2is a load-bearing conveyor element, for example, in particular aconveyor belt such as a continuous flow conveyor for example, which isused in areas in which low ambient temperatures prevail, especially inan area where deep-freezing is taking place. Naturally, thetemperature-regulated drive element 2, such as a band, belt or similar,may also be used as a timing belt on machinery incorporating the movingunit 1. As illustrated, at least one module 12 is provided, extendingacross at least a part of the length of the drive element 2, by means ofwhich the pre-definable minimum temperature of the drive element 2 ismaintained by applying energy by a system which involve contact. In thisspecial application, the module 12 has at least one means 27, forexample several rollers 28, abrasive strips or similar, which createinternal or external frictional energy between the drive element 2 andthe means to generate heat.

Rollers 28, in particular friction rollers, are expediently disposed ata distance apart from one another in the longitudinal direction andengage with the two mutually remote running and top layers 6, 7, whichcauses a maximum permissible deformation in at least certain regions ofthe drive element 2, creating an increase in temperature depending onthe peripheral speed of the drive element 2 and the deformation energygenerated. The rollers 28 spaced apart by a thickness in thelongitudinal extension of the drive element 2 are designed so that theycan be displaced relative to one another, so that a reduction in thedistance corresponding to the thickness of the drive element 2 willinduce an increase in the deformation energy. In order to operate thisdisplacement, at least one but preferably several rollers 28 in thedirection perpendicular to the feed motion—indicated by arrow 5—areconnected to the control unit 15 via a displacement drive, notillustrated. The at least one actual value of the temperature of thedrive element 2 is detected by at least one measuring means 17 connectedto the control unit 15 and transmitted to the control unit 15 in theform of data, where it is processed in the control algorithm to obtain acontrol variable for the parameter, in particular to adjust a distanceas measured between oppositely lying rollers 28. As a result, the module12 for transmitting energy is then activated by the control unit 15whenever the actual value of the temperature of the drive element 2falls below the threshold value for the minimum temperature in thepositive temperature range or exceeds an upper threshold value.

An optimum setting in is one where the rollers 28 are spaced apart oneabove the other at a distance that is only slightly smaller than themaximum thickness of the drive element 2 and the peripheral speed isincreased to a maximum. Naturally, the rollers 28 may also be heated andthe heat energy transmitted to the drive element 2 by contact or heattransmission. To this end, the rollers 28 are made from a material thatis a good heat conductor. In order to provide the means 27 with a largerheat-transmitting surface area, it would also be possible to provide therunning and top layers 6, 7 respectively with at least one heatedabrasive strip instead of using rollers 28. The temperature of the driveelement 2 can be detected without contact or by means of at least oneother measuring means 17, not illustrated.

FIGS. 7 and 8, which will be described together, provide highlysimplified, schematic diagrams illustrating another variant of thedevice 11 co-operating with the moving unit 1. As explained in detailabove, the moving unit 1 has at least one driving member 3, and at leastone driven member 4, by means of which the drive element 2 can be movedalong at a pre-definable peripheral speed and in a pre-definable feedmotion and feed direction—indicated by arrow 5. In this embodiment, thetemperature is regulated by applying energy by means which involvecontact. It is preferable to use an endlessly circulating V-belt forthis embodiment, with a substantially trapezoidal or V-shaped crosssection, in which belt running faces 30 bounded by belt pulley runningfaces 29 converge with one another at an angle in the direction of arotation axis 31. The drive element 2 also incorporates the top layer 7overlapping with the running layer 6, between which the traction layer 8with the strengthening supports 9 is disposed.

The strengthening supports 9 are made from an electrically conductivematerial. At least some of the strengthening supports 9 are designed sothat they constitute electrical contacts 32 in the region of the beltrunning face 30 which link up with contact points 33 disposed at leastin a part-region of the belt pulley running faces 29 in order to supplyelectrical energy. As a result of the belt tension relative to the beltpulley and due to the at least looping connection between the contacts32 and contact points 33, a conductive connection is established inorder to regulate the temperature of the drive element 2. A surface ofthe contact points on the belt pulley-side extends parallel with and inplanar arrangement with respect to the belt pulley running face 29, soas to avoid any adverse effects on the circumferential forces to betransmitted. Naturally, the belt pulley may also be designed so that aperipheral zone surrounding the core zone of the belt pulley facing thedrive element 2 is made from a conductive material, whilst the core zoneis made from an insulating material, in particular plastic, for examplepolyurethane. By providing the belt pulley with this multi-partstructure, no electric current will be transmitted to other machineparts. The structural design as well as the different materials whichmay be used for the belt pulley are already known from the prior art.

Another way of establishing a reliable contact between the belt-sidecontacts 32 and the contact points on the belt pulley is to design thecontact points 33 as resiliently elastic elements, which stand proud ofthe belt pulley running surfaces 29 when the drive element 2 is in theslack state and the contact points 33 are not pushed by the contacts 32against their bias until the pre-selectable tension of the drive element2 is applied relative to the belt pulley, thereby producing the planarsurface again. Accordingly, the positive potential is applied to thedriving member 3 forming the first module 12 and the negative potentialis applied via the other module 12 constituting the driven member 4.

The driving and/or driven member 3, 4 forming the module 12 maynaturally also permit the contactless supply of energy for regulatingthe temperature as described in respect of FIGS. 1 to 5, in which caseone or more induction coils 13, not illustrated, or the microwavegenerator 26 will be provided in or on the belt pulley and current orvoltage induced in the strengthening supports 29 and the loop 10 formedby them. In this embodiment, at least one measuring means 17 is providedin the form of a pyrometer, not illustrated, installed at a slightdistance from the drive element 2, by means of which the actual value ofthe temperature is detected without any contact.

FIG. 9 is a highly simplified, schematic diagram illustrating anotherembodiment of the moving unit 1 and the device 11 co-operating with it.The device 11 has two separately installed modules 12, one of themodules 12 being provided in the form of an induction coil 13 whichco-operates with the strengthening supports 9 of the drive element 2 asexplained in detail above, and the other module 12 being a heatingelement which operates without contact. The latter module 12 may be aheat exchanger or similar using the heat radiated from the module 12, inparticular a drive 34, and in the case of a drive 34, the dissipatedheat is used to regulate a temperature and maintain a pre-definableminimum temperature in at least certain regions of the drive element 2.As a result of the irradiated heat energy, a flow of heat 35 can beapplied to at least certain regions of the drive element 2, thereby alsoenabling energy to be supplied in this application without contact.

It should be pointed out that this stage that the module 12 maynaturally also be arranged so that it can be displaced relative to thedrive element 2, which means that the drive element 2 can be heated atleast to a run-up temperature that is lower than a minimum temperatureso whilst the drive element 2 is stationary, for example during a dwelltime when a moving unit 1 is in a standby position, and during operationby increasing the energy or power delivered to the drive element 2and/or by switching on another module 12 which sets the pre-settableminimum temperature within a pre-settable time via one or preferablyseveral measuring means 17, after which the actual value of theinstantaneous temperature of the drive element 2 is detected in at leastcertain regions and at certain times and compared with a pre-set desiredvalue of the minimum temperature, and if the measured actual temperatureis found to deviate from the pre-definable desired value or if theactual value of the minimum temperature deviates from at least onepre-set threshold value for the minimum temperature, the requisiteparameters are applied to at least one of the modules 12, such asfrequency, current amplitude, power, etc., in order to adapt thetemperature to the desired value of the minimum temperature. An optimumsetting can be obtained and above all the optimum minimum temperaturecan be maintained, once it has been set, by the closed-loop automaticcontrol circuit and by detecting the actual values at leastintermittently under all operating conditions and taking account of theambient influences, such as ambient temperature, air humidity, etc.

Let us take the example of a situation where a temperature of −20° C.and an air humidity of 60% prevails in the ambient environment, forexample in a cold-store of a warehouse or outside a building. Themachine part 20 displaceable by the drive element 2 has to be displacedat a speed of 5 m/sec. By employing the invention, the ambientinfluencing factors and/or at least one operating factor can be takeninto account in the control algorithm used to compute and define thedesired value or threshold value for the minimum temperature of thedrive element 2 under these conditions, which might be +15° C. forexample, and at least one parameter is changed during operation of themoving unit 1, such as the frequency of the induction coil 13 or themicrowave generator 26, the heat output of a module 12 which transmitsenergy without contact, the amplitude of the current flowing through thestrengthening supports, or the distance between oppositely lying rollers28, until the optimum minimum temperature is reached and set. To thisend, it is necessary to detect intermittently at least one actual valueof the temperature in a section of the drive element 2 by means of atleast one measuring means 17 and this is then forwarded to the controlunit 15. As a result, the module 12 will then be activated by thecontrol unit 15 so as to emit or generate or transmit energyintermittently if the actual value of the temperature of the driveelement 2 is below the threshold value of the minimum temperature of+15° C., for example, in the positive temperature range and/or above theupper threshold value of +25° C., for example, in the positivetemperature range. If the drive element 2 has to be heated to atemperature of preferably +15° C. when the moving unit 1 is operating at−20° C., for example, the actual value of the temperature of the driveelement 2 is detected by the measuring means 17 in cycles. If the actualvalue of the temperature corresponds to or falls below the pre-definablelower threshold value of +15° C. for the minimum temperature, forexample, at least one parameter such as the frequency of theinduction-coil 13 will be changed until-the drive element 2 reaches theminimum temperature of +15° C. again. The drive element 2 therefore hasto be heated by applying energy and to do this it is necessary to supplyonly some of this energy because the drive element 2 can be heated tothe pre-set minimum temperature across its entire length and/orthickness due to the relative displacement between the module 12 and thedrive element 2. Naturally, it would also be possible to set a positivetemperature range for the minimum temperature, for example +15° C. bis+25° C., defined by the lower and upper threshold value of the minimumtemperature. If the upper threshold value for the minimum temperature isreached, for example +25° C., energy will cease to be transmitted viathe module 12 until the detected actual value of the minimum temperaturedrops to +15° C. for example, after which the energy applied will beregulated to maintain the minimum temperature of +15° C., for example.

Naturally, it would also be possible to define the parameters of themodule 12 for a specific application, in which case it will still bepreferable to use the embodiment described above. For example, thefrequency of the induction coil 13 needed to obtain the minimumtemperature of +18° C., for example, at an ambient temperature of −20°C., for example, can be set so that it essentially can not be changed.The advantage of this embodiment is that no measuring means 17 areneeded to detect the actual value of the temperature of the driveelement 2.

As indicated in FIG. 2, another embodiment of the invention offers theoption of providing at least one electrically conductive film 36 in thedrive element 2 to form the loop 10 which transmits the induced voltageor the induced current. The loop 10 of electrically conductive film 36may be endless or non-endless and has a slimmer thickness than thethickness of the drive element 2, which means that the method proposedby the invention can also be used with drive elements 2 of lesserthicknesses. Using standard aluminium films, for example, it would bepossible to make loops 10 with a thickness of between 2 μm and 30 μm.Alternatively, the loop 10 may also be made from an electricallyconductive film 36 of copper, between 100 μm and 200 μm thick. Finally,it would also be possible to make the loop 10 from an electricallyconductive film 36 made from a steel alloy or spring steel. The loop 10obtained by the film 36 is preferably flat and extends along at least apart of the length and width of the drive element 2. Naturally, the film36 may also constitute the strengthening supports 9, which obviates theneed to provide additional strengthening supports 9. The film 36 mayalso be a plastic film coated with metal, in which case the metalcoating may be printed or vapour-deposited on the plastic film.

It should be pointed out that the structure and operating mode of themoving units 1 with their drive elements 2 described above are given byway of example only. It would also be possible for the drive element 2to be made without any strengthening supports 9, for example. The sameapplies to the design and layout of the modules 12. The module ormodules 12 may be mounted at any point, such as to the side and/or aboveand/or underneath the drive element 2.

For the sake of good order, it should be pointed out that, in order toprovide a clearer understanding of the structure of the moving unit anddevice, they and their constituent parts are illustrated to a certainextent out of scale and/or on an enlarged scale and/or on a reducedscale.

The independent solutions proposed by the invention and the associatedobjectives may be found in the description.

Above all, the subject matter of the individual embodiments illustratedin FIGS. 1, 2, 3; 4; 5; 6; 7, 8; 9 may be construed as independentsolutions proposed by the invention in their own right. The objectivesand associated solutions may be found in the detailed descriptions ofthese drawings.

LIST OF REFERENCE NUMBERS

1 Moving unit 2 Drive element 3 Driving member 4 Driven member 5 Arrow 6Running layer 7 Top layer 8 Traction layer 9 Strengthening supports 10Loop 11 Device 12 Module 13 Induction coil 14 Connecting line 15 Controlunit 16 Energy field 17 Measuring means 18 Bearing and retainingmechanism 19 End region 20 Machine part 21 Guide mechanism 22 Guide rod23 Support strip 24 Passage 25 Liquid 26 Microwave generator 27 Means 28Roller 29 Belt pulley running surface 30 Belt running surface 31Rotation axis 32 Contact 33 Contact point 34 Drive 35 Heat flow 36 Film

1. Method of regulating a temperature of a drive element (2), such as aband, belt or similar, employed in applications involving freezing ordeep-freezing, whereby at least a part-region of the drive element (2)is heated by means of a module (12) generating and/or transmittingenergy, characterised in that the actual value of the temperature of thedrive element (2) is detected and, whenever the actual value of thetemperature deviates from at least one pre-set threshold value for theminimum temperature, the module (12) is activated by a control unit (15)in order to supply energy so that the drive element (2) is adjusted to apre-definable minimum temperature and maintained at a pre-definableminimum temperature.
 2. Method as claimed in claim 1, characterised inthat an electrically conductive loop (10) in or on the drive element (2)supplies energy in order to maintain the minimum temperature.
 3. Methodas claimed in claim 1, characterised in that the minimum temperature ofthe drive element (2) is maintained by supplying energy by means whichinvolve no contact or involve contact.
 4. Method as claimed in claim 1,characterised in that the minimum temperature of the drive element (2)is maintained by delivering energy from a module (12) radiating heat, inparticular a drive (34), optionally via an inter-connecting heatexchanger.
 5. Method as claimed in claim 1, characterised in that theminimum temperature of the drive element (2) is maintained by applyingthe heat dissipated by the module (12).
 6. Method as claimed in claim 1,characterised in that the minimum temperature of the drive element (2)is maintained by means (27) acting in or on the drive (2) elementgenerating frictional energy, for example friction rollers, abrasivestrips.
 7. Method as claimed in claim 1, characterised in that a liquid(25) with a high boiling point is circulated through the drive element(2) and the minimum temperature of the drive element (2) is set andmaintained by applying wave energy from the module (12).
 8. Method asclaimed in claim 1, characterised in that the stationary drive element(2) is heated to a pre-definable temperature.
 9. Method as claimed inclaim 1, characterised in that at least certain regions of the driveelement (2) of a displacement system (1) are pre-heated whilst it isstationary and at least certain regions are adjusted to a pre-definableminimum temperature during operation, after which this set minimumtemperature is maintained.
 10. Method as claimed in claim 1,characterised in that at least one control algorithm is used to set theminimum temperature so that the minimum temperature of the drive element(2) can be maintained at least almost substantially constant.
 11. Methodas claimed in claim 1, characterised in that the drive element (2) isfed past or fed through at least one energy field (16).
 12. Method asclaimed in claim 11, characterised in that the energy field (16) is amechanical or magnetic or electrical or electromagnetic field. 13.Method as claimed in claim 11, characterised in that the electromagneticfield is preferably a medium-frequency or high-frequency alternatingfield.
 14. Method as claimed in claim 1, characterised in that at leastone energy field (16) or energy is applied intermittently to at leastcertain regions of the drive element (2) across a major part of,preferably its entire, length in order to maintain the minimumtemperature.
 15. Method as claimed in claim 1, characterised in that themodule (12) supplying energy to the drive element (2) is activated orswitched off when prompted by the control unit.
 16. Method as claimed inclaim 11, characterised in that the energy field (16) is an eddy currentor a voltage induced in the loop (10) and heat is generated as thecurrent flows through the loop (10).
 17. Method as claimed in claim 11,characterised in that the energy generates heat as the current flowsthrough the loop (10).
 18. Method as claimed in claim 11, characterisedin that energy is applied directly to the loop or by means of the energyfield (16) outside of the loop (10) and actively linked to it. 19.Method as claimed in claim 11, characterised in that the actual value ofthe temperature of the drive element (2) is determined at leastintermittently or at certain sections.
 20. Method as claimed in claim11, characterised in that the actual value of the temperature of thedrive element (2) or the induced voltage or the induced current isdetected by a measuring means (17) and transmitted to a control unit(15) and whenever the actual value of the minimum temperature deviatesfrom at least one pre-set threshold value for the minimum temperature,the control unit (15) regenerates a signal for further processing oroutput in or on the control unit (15).
 21. Method as claimed in claim 1characterised in that the actual value of the minimum temperature ispre-set by an operator or by means of a control algorithm and the energysupply to the drive element (2) by the module (12) is regulated. 22.Moving unit (1), in particular for applications involving freezing ordeep-freezing, having a drive element (2), such as a band, belt orsimilar, and a machine part, the drive element (2) and the machine partbeing mounted so as to be displaceable relative to one another, and atleast one module (12) which generates and/or transmits energyco-operates with the drive element (2) in order to heat at least certainregions of the drive element (2), in particular by applying the methodas claimed in claim 1, characterised in that the module (12) extendsacross a part of a length of the drive element (2) and at least onemeasuring means (17) co-operates with the drive element (2) in order todetect an actual value of the temperature of the drive element (2) andis connected to a control unit (15) which activates the module (12). 23.Moving unit as claimed in claim 22, characterised in that the module(12) is provided in the form of at least one induction coil (13) or atleast one microwave generator (26) for generating an energy field (16)or heat flow (35) actively connected to the drive element (2). 24.Moving unit as claimed in claim 22, characterised in that the module(12) is provided in the form of a heating device, such as a heatingcoil, or a heat-radiating element such as a heat exchanger, fan heater,in order to generate a thermal energy field which is actively connectedto the drive element (2).
 25. Moving unit as claimed in claim 22,characterised in that the module (12) is disposed on or in the machinepart (20) or is constituted by the latter.
 26. Moving unit as claimed inclaim 22, characterised in that the drive element (2) has at least oneloop (10) made from electrically conductive material.
 27. Moving unit asclaimed in claim 26, characterised in that the loop (12) is provided inthe form of at least one strengthening support (9) extending across thelength of the drive element (2).
 28. Moving unit as claimed in claim 26,characterised in that the loop (10) is provided in the form of at leastone electrically conductive film (36), in particular a copper film, afilm (36) of steel alloy or spring steel, extending across the lengthand at least across a part of a width of the drive element (2). 29.Moving unit as claimed in claim 26, characterised in that the driveelement (2) incorporates the strengthening support (9) and/or the film(36) and the strengthening support (9) and/or film (36) is made fromelectrically conductive material.
 30. Moving unit as claimed in claim26, characterised in that the loop (10) has a coil.
 31. Moving unit asclaimed in claim 27, characterised in that at least one of thestrengthening supports (9) acts as a ferromagnetic core, in particularan iron core.
 32. Moving unit as claimed in claim 27, characterised inthat the strengthening support (9) is made from aramide or steel andglass fibre.
 33. Moving unit as claimed in claim 22, characterised inthat the module (12) is disposed externally to the drive element (2) andis stationary or is displaceable relative to the drive element (2) inthe direction extending parallel with or transversely to the loop (12).34. Moving unit as claimed in claim 22, characterised in that the module(12) extending at least substantially around the drive element (2) isprovided in the form of primary induction coil (13) which is preferablydisposed perpendicular to a feed direction (5) of the drive element (2),and the loop (10) actively connected to the induction coil (13) forms asecondary coil.
 35. Moving unit as claimed in claim 23, characterised inthat at least one module (12) for generating the energy field isprovided on, in or inside a housing-type casing surrounding the driveelement (2).
 36. Moving unit as claimed in claim 23, characterised inthat a frequency and/or current amplitude of the induction coil (13) towhich alternating current is to be applied is adjusted depending on aminimum temperature, in particular an operating temperature, of thedrive element (2).
 37. Moving unit as claimed in claim 22, characterisedin that the drive element (2) has at least one passage (24) preferablyextending across the length and across a part of the width thereof foraccommodating a liquid (25) with a high boiling point and wave energygenerated by the module (12) can be applied to the heat-transmittingliquid (25) with a high boiling point.
 38. Moving unit as claimed inclaim 22, characterised in that the moving unit (1) incorporates anothermachine part and the other machine part is guided on a guide mechanism(21) and can be displaced by the drive element (2).
 39. Moving unit asclaimed in claim 22, characterised in that the moving unit (1) has atleast one driving and driven member (3, 4), in particular discs, made atleast partially from electrically conductive material for deflecting theendless drive element (2) and a positive potential is applied to one ofthe discs and negative potential is applied to the other disc, andelectric contacts (32) are provided on the drive element (2) fortransmitting the preferably electrical energy between the discs and thecontacts (32) as a result of contact.
 40. Moving unit as claimed inclaim 39, characterised in that the peripheral zone facing the driveelement (2) and surrounding a core zone of the disc is made fromelectrically conductive material and the core zone is made from aninsulating material, in particular plastic.
 41. Moving unit as claimedin claim 26, characterised in that a closed loop (10) of the preferablynon-endless stationary drive element (2) is preferably connected bywires via electrical contacts, in particular terminal contacts, to apower source generating current, in particular a direct current sourceto enable current to be applied.
 42. Moving unit as claimed in claim 22,characterised in that the drive element (2) is a flat belt or V-belt orcogged belt.
 43. Moving unit as claimed in claim 22, characterised inthat the drive element (2) has a running layer (6), a top layer (7) andat least one traction layer (8) disposed in between and at least oneloop (10) and/or film (36) of electrically conductive material isdisposed in the traction layer (8).
 44. Moving unit as claimed in claim22, characterised in that at least one measuring means (17), fordetecting the temperature of the drive element (2) is disposed in ordirectly on the drive element (2) and is provided in the form of astrain gauge, thermocouple or pyrometer in particular.
 45. Moving unitas claimed in claim 44, characterised in that the measuring means (17)is connected to the control unit (15) and the control unit (15) has acontrol algorithm for at least regulating the temperature and/or theperipheral speed and feed rate of the drive element (2).